Distillation of oxygenated organic compounds



March 1 c. E. MORRELL ET AL 2,583,272

DISTILLATION 0F OXYGENATED ORGANIC COMPOUNDS Original Filed Dec. so,1947 a Sheets-Sheet 2 HYDQOCAQEONE:

GAQEONYLS ALDEHYDEE: ESTERS 4.0(9 Gouosussfls io9 H0 iOi- -iii 105 FEEDi z --F2AQT\ouAToQs- I 1151' i0? ALCOHOUB l AQoEoos A00 Eo'rToMs L BnCLtmov'nez March 1952 c. E. MORRELL ET AL DISTILLATION OF OXYGENATEDORGANIC COMPOUNDS 3 Sheets-Sheet 5 Original Filed Dec. 30, 1947 mmmkmmmmorImnq mJriO matqu Q200m u0d0 1 WQUmIMO 2 OD sow s w u D e n m w w n n5 Q N. e n FEM O h mm 5% 5 7 3 3 r v6 am cc? no Patented Mar. 4, 1952UNITED STATES PATENT OFFICE DISTILLATION' OF OXYGENATED ORGANICCOMPOUNDS Charles E. Morrell, Westfield, Carl S. Carlson, Roselle, andPaul V. Smith, J r., Westfield, N. J assignors to Standard OilDevelopment Company, a corporation of Delaware Original applicationDecember 30,,1947,,.Serial No.

794,589. Divided and this application, Decemher 1, 1950, Serial No.198,522

8 Claims.

1 This application is a division of U. S. patent application Serial No.794,589 filed December 30, 1947, now Patent No. 2,551,625, granted May8, L951.

This invention relates to a practical method of 5 rate the mixture intoa plurality of narrow-boilseparating wide boiling mixtures of oxygenateding cuts and then distill each: of these cuts in organic compounds andis concerned with the thep-resence of a large molar excess of water, ascontrolled use of water or solvents of high water described incopencling' application Serial No. content as a refluxing medium in acontinuous 724,840 filed January 28, 1947, now Patent No. fractionaldistillation of such wide-boiling mix- 1 2,551,593 granted May-.8, 1957;However, sucha tures. process requires a large number of operations toWide-boiling mixtures of oxygenated organic produce specificationproducts from theoriginal compounds may be obtained for example by themixture. Furthermore, undesirable components Fischer synthesis in whichcarbon monoxide is of the original mixture. find their way into thereacted with hydrogen to produce a mixture of individual cuts causingdifiiculty in their efiicient hydrocarbons and oxygenated organiccomseparation. In addition, during the preliminary pounds which separateinto an oil layer and a distillation into closeeboiling cuts, chemical,rewater layer, both of which contain various hyactions often occurwhich destroy valuable comdrocarbons, ketones, aldehydes, ether-s,acetals, ponents. For example, the alcohols react with ketals, esters,carboxylic acids, primary, secondketonesandaldehydes, formingketalsand'acetals ary and tertiary alcohols of a wide range ofrespectively; The aldehydes likewise undergo molecular weights. Stillanother source of these aldolization.

Wide-boiling mixtures f oxy n r n It: is therefore an object of thisinvention to p un s s in the products of Y provide acommerciallyfeasible process for the oxidation Where both Oil Wa r l y s a eeflicient separationv of wide-boiling mixtures of obtained both of whichcontain oxygenated orgx-ygenatedj organic cgmpounds which we m, garlicCompounds A typical example of the cult to-separate by ordinaryfractional distillatcomposition of a water layer obtained in themonmethodg Fischer Process is as follows: It is'a further object of thisinvention to pro- Weight per cent vide a process which minimizes orpreventsthe Water 90-1 loss of valuable components. Alcohols: Thepresent invention is madepossible by the Methyl, ethyl, normal andisopropyl, discovery that when a mixture of oxygenated Secondary,tertiary and 150- compounds, such as those mentioned above, are ynormal, Secondary, tertiary and fractionally distilled in the presenceof a surfiisoamyl, etc ciently large volume percent of aqueous reflux,Aldehydesi the volatilities of the oxygenated compounds: areAceta-ldehyde, plopironaldeklyde, butyraltered to such an extent thatseparations which aldehyde, normal and lsovalemlde' were impossible byordinary fractionation become hyder etc 40 possible in the presence ofthe excess water, and Ketones: chemical reactions which occur in the:absence Acetone methyl ethyl ketone; methyl; of water are substantiallyprevented. The aquepro pyl kefione methyl lsopmpyl ous reflux used maybe water or other solvents ketonei methyl normal buiPyl W of high watercontent, such as aqueous solutions methyl lsobutyl ketone' methyl keofsalts as the chlorides, nitrates, sulfates, ,ace- Fone, etc tates, etceteraof sodium, potassium, ammonium Esters v and the like, dilute acidssuch as those obtained Ethyl t 01ml P1PY1 acetate by distilling. thecrude water layer from the 23 proplonate' etc 2' Fischer synthesis etcetera. Hy i 5 -Z The following table lists the relative volatilityEthers Trace of mixtureso various oxygenated organic com- Theseparationof such a complex mixture is pounds with reference-to ethanolat the indicated water concentrations.

Table I Volatility Relative to Ethanol at Indicated Water Concentration1 Normal Volatility M01 per cent water n-Valeraldehyde n-ButyraldehydeMethyl propyl ketone Methyl ethyl ketone Acetone t-Butanol. s-Butanol.Isopropano LButanoL...

Methanol 1 The relative volatility is the volatility of one componentdivided bythat of the other, the volatility of each component beingproportional to its partial pressure divided by its mol fraction in theliquid phase. It is also defined by the equation: alpha: (y lyg) /1where 1 refers to the vapor phase mol fractlons of the components to beseparated, subscript 1 designates the more volatile components andsubscript 2 the less volatile components. The data in theabove tableindicate quite clearly that the large proportion of water present in theliquid phase as a refluxing medium alters the relative volatility of themixed organic oxygenated compounds to such an extent that separation canbe easily secured.

To obtain the desired separation of purified organic components frommixtures, such asthose mentioned with the benefits of the presentinvention, the mixture is subjected to a continuous fractionaldistillation in a column of practical size, including a rectificationzone and a stripping zone forcountercurrent vapor-liquid contact underreboiling and refluxing conditions. A sufficiently large quantity ofwater is introduced into an upper part of the rectification zone toeffectively modify the relative volatilities of the organic compounds tobe separated. The separation can be effected in a continuous mannerunder steady state conditions to obtain product streams of desiredpurities and constant compositions while supplying the large quantity ofWater in the upper part of the rectification zone. The temperature ofthe water introduced in the rectification zone is preferably close tothe temperature of the liquid on the feed plate, although it may belowered to partially condense vapors ascending to the water feed plate.Since the efiicient separation is essentially continuous, Water has tobe added continuously near the top of the fractionating column while themixture of oxygenated organic compounds to be separated is fedcontinuously into the column at a lower point and while suificient heatis provided to afford distillation throughout the column.

The feed stream of the oxygenated organic compounds is preferablyintroduced into a fractionating column between an upper rectificationsection and a lower stripping section at a point where pletely vaporizedwhen introduced into the fractionation tower.

Vapors of the organic compounds introduced in the feed stream at thebottom part of the rectification zone in the fractionating column passup the rectification zone in contact with descending internal liquidreflux under practically equilibrium boiling and refluxing conditions.

The quantity of water required to be introduced continuously at theupper part of the rectification zone for accomplishing the desiredseparation of the wide-boiling compounds is considerably greater thanthe quantity of condensate with which it becomes homogeneously mixed.This is necessary in order to make the water concentration of theinternal reflux substantially above a critical minimum in the range of65 to mol per cent. With adequate water concentration in the internalreflux for effecting the separation, the organic component to beisolated in the aqueous bottoms is dissolved in the aqueous internalreflux that reaches the bottom part of the rectification zone andfinally the bottom of the stripping zone.

Due to the fact that water, considerably in excess of the waterdistilled, is introduced to mix with the condensate near the top of therectification zone, the water concentration in the internal reflux atthe top of the rectification zone is higher than the water concentrationin the vapors passing up through the zone. Contrasted therewith, in thenormal rectification of oxygenated compounds from an aqueous feed, thewater concentration diminishes rapidly toward the limiting waterconcentration of the aqueous azeotropes in the vapors ascending thefractionation tower.

The minimum water concentration in the internal reflux for obtaining theseparation depends on the particular organic compounds in the originalmixture. Generally essentially no separation is effected if the internalreflux contains less than 65 mol percent water; and for obtainingsatisfactory results on a practical scale more 7 than 85 mol percent ofwater, preferably to 99 mol percent water is required in the internalreflux. As the water dilution of the internal re-' flux becomesinfinite, the selectivity of the separation becomes increased but theefficiency is excessively lowered on account of the relatively smallquantities of the organic compounds involved.

Under steady state conditions in the fractionation or distillation zone,the internal reflux having adequate water concentration foraccomplishing the separation of wide-boiling mixtures tends to have anearly constant water concentration in the homogeneous liquid phase ateach plate except in cases where a very dilute feed is used such as thecrude water layer. In any case operation with different waterconcentration in the stripping and enriching zones is quite feasible.This internal reflux in flowing from the top to the bottom becomesricher in the components found least volatile while the other organiccomponents of the feed become distilled overhead.

The overhead vapors from the rectification zone are enriched in one ormore of the organic components rendered relatively more volatile by thehigh water concentration in the liquid reflux while the remainingportion of the organic material introduced with the feed is dissolved inthe internal reflux.

The functioning of the stripping zone may be described as follows:

The dilute aqueous solution of the wide boiling compounds to beseparated, as in the liquid reflux from the bottom of the rectificationzone, flows downwardly through the stripping zone in countercurrentcontact with ascending vapors evolved from the solution under reboilingconditions. A sufficiently high concentration of Water is maintained inthe liquid flowing down through the stripping zone as in therectification zone, to make the liquid progressively richer in thosecomponents made less volatile while the remain ing components arestripped from the liquid. Under essentially equilibrium reboiling andrefluxing conditions in the stripping zone, the more volatile componentsmay be removed as vapor overhead from the stripping zone at the samerate that those components enter the stripping zone as part of theliquid feed to this zone and a dilute aqueous solution of the lessvolatile components freed from the more volatile com ponents may bewithdrawn from the bottom part of the stripping zone.

The above principle can be applied not only to I the crude water layerwhich is obtained by simple separation from the Fischer synthesis unitbut can also be applied to oxygenated compounds recovered from the oillayer by a separate operation involving washing of the oil with water orsome polar solvent. It can also be applied to products recovered fromthe recycle or exit gases from the synthesis step by scrubbing withwater or a polar compound or to mixtures of these oxygenated compoundsrecovered from the oil layer with the crude water layer.

According to one embodiment of this invention distillation is carriedout, as described above, under such conditions that the overhead fromthe distillation zone consists predominantly of free of loweralcoholconstituents present in the crude organic mixture fed to the column.

By this type of distillation it is possible to segregate the crudeorganic products from a Fischer synthesis operation in such a mannerthat a mixed alcohol-acid residue essentially free of or greatlydepleted in aldehydes, ketones, esters, hydrocarbons, ketals and acetalsis obtained. The overhead besides containing esters, hydrocarbons andethers in minor amounts, will consist largely of acetaldehyde,propionaldehyde, acetone, methyl ethyl ketone, butyraldehyde togetherwith smaller amounts of aldehydes and ketone containing 5 and 6 carbonatoms.

Another embodiment of this invention is to so regulate operatingconditions as regard heat (input), reflux ratio, feed rates, etc., to adis tillation column of the above-described type so that, in addition tothe carbonyls, etc., essentially a major portion of branched chain andsecondary and tertiary alcohols present in the hydrocarbon synthesiswater layer are recovered overhead. These branched alcohols consist forthe most part of isopropyl and secondary and tertiary butyl alcohols. Bythis means it is possible to obtain as bottoms a water solution of acidtogether with primary alcohols of 1 to 5 carbon atoms essentially freeof or greatly depleted in aldehydes, ketones, esters, acetals,hydrocarbons, ethers andsecondary alcohols. In such an operation the keycomponents will probably be the lowest secondary alcohol, namely, isoropyl and the higher primary alcohols such as normal amyl alcohol. Undercertain conditions it may be desirable to obtain good recovery ofall theprimary alcohols in the bottom stream even if this leads to incompleterecovery of the branched alcohols in the overhead. However, it ispreferred to operate so as to obtain relatively complete removal of thebranched alcohols, especially isopropyl, from the column bottoms even atsome sacrifice in the recovery of the primary alcohols especially C4 toC6 in the bottoms stream. In other words, in order to obtain completeremoval of the isopropyl from the ethyl, it may be desirable to takeoverhead some of the normal butyl and higher normal alcohols.

It is also within the scope of this invention to preliminarily distillthe aqueous layer from the Fischer synthesis to take overhead all of thematerials lighter than the acids, leaving an aqueous acid bottoms andthen apply the principles of this invention to the overhead cutcontaining only the neutral oxygenated compounds. There is an advantagein this method of operation in that the material in the stripping zoneis not diluted with as large amount of water and consequently betterseparation can be obtained under certain conditions.

It is also possible to apply this type of operation to a crude aqueoussolution of oxygenated compounds from the Fischer synthesis, which hasbeen stripped before the distillation to ,re-

cover overhead as much as possible of the compounds more volatile thanthe alcohols. In other words, it can be applied to a crude aqueoussolution of oxygenated compounds which has been previously stripped ofall volatile materials boiling below methyl, ethyl and isopropylalcohols.

When operating according to the above procedures, the presence of largequantities of water in the feed may make it diflicult to completelyeliminate the non-alcoholicconstituents without taking off some of thenormal alcohols overhead. The preliminary topping of the crude waterlayer to separate the neutral compounds from the acids helps to overcomethis difficulty to some extent but complete elimination of normalalcohols from the overhead cannot be effected even by this expedient ifall of the non-alcoholic constituents are removed. It is thereforeproposed, in still another embodiment of this invention, to overcomethese difiiculties by first separating the crude aqueous product fromthe Fischer synthesis or the acid-free neutral compounds resulting fromthe above-mentioned preliminary distillation into two fractions, onecontaining all compounds boiling below normal butyl alcohol and theother containing all compounds boiling in the range of normal butylalcohol and higher. Each of these fractions is then extractivelydistilled with large quantities of water as described above to remove anoverhead fraction containing the non-alcoholic constituents. Undercircumstances in which it is not necessary to separate the secondary andisobutyl alcohols completely from the normal alcohols, it may bedesirable to operate the distillation column in such a manner that someor all n-propyl alcohol is removed in the bottoms.

The bottoms from any of the above methods of operation, containing theacids and/or other oxygenated compounds, principally alcohols, may beworked up in a variety of ways to recox er therefrom the alcohols andother compounds present. The overhead from such distillations which arerich in carbonyl compounds and esters together with a small amount ofalcohols and hydrocarbons also may be worked up in a variety of ways.

In the accomplishment of the foregoing and related ends the inventionthen comprises features hereinafter described and particularly pointedout in the claims, the following description and antnpxed drawingssetting forth in detail certain illustrative embodiments of theinvention, these being indicative, however, of but a few of the variousWays in which the principle of the invention may be employed.

Figure 1 of the drawing illustrates a flow plan of a unit for obtainingseparation of a wideboiling oxygenated organic compound mixture.

Figure 2 illustrates a flow plan of a modification of the process shownin Figure 1.

Figure 3 illustrates a flow plan of a modification of the process shownin Figure 2.

Referring to Figure 1, I represents a fractional distillation column inthe interior of which is provided means for obtaining efficientcountercurrent liquid vapor contact, e. g. such conventional means asbubble plates or packing and 2 represents a similar tower for separatingthe overhead from tower I into additional fractions while 3 and 4represent towers for effecting better separation of the products fromthe bottom of tower I.

This invention will be described in detail as applied to the separationof a mixture of wideboiling oxygenated organic compounds from the totalwater layer obtained in the Fischer synthesis process, such a waterlayer having the composition given above.

Referring to the drawing, a fraction of the above composition obtainedin the Fischer synthesis is introduced by line 5 into the midpoint ofcolumn I where it is fractionated in the presence of a stream of liquidwater introduced through line 6. Conditions are maintained in tower Isuch as to cause distillation of the oxygenated compounds in thepresence of the water on each plate of the tower. A suflicient amount ofwater is added so that it is present to the extentof 90 mol percent oneach plate. As the vapors of the feed pass up the column some of themare dissolved in the large excess of water descending the column and arecollected together with the water in pools on each plate.

Conditions are maintained on each plate of the tower such that liquidmixtures of the oxygenated compounds are at their boiling points and arecontinuously being contacted with vapors boiled from the plates below.Because of the reversal of volatility in many cases many of thecomponents which would otherwise remain in the liquid are renderedvolatile. By maintaining the amount of water on each plate so large thatinfinite dilution is approached, the optimum relative volatilities forthe separation of the desired components can be secured. Furthermore, bycontrolling the amount of oxygenated com pounds in the reflux, thereflux ratio, and the number of plates, the actual degree of separationmay be varied until the desired product purity and recovery areobtained. Accordingly, conditions are maintained so that carbonyls,esters, hydrocarbons, acetals and ethers are removed overhead as vapor.

Overhead vapors consisting essentially of carbonyls, esters,hydrocarbons (if present) and ethers are withdrawn from the top ofcolumn I through line I by which they are passed through condenser 8 toa receiver 9. A portion of condensate collected in receiver 9 isreturned to the top part of column I as external reflux through line I0.The remaining portion of distillate collected in receiver 9 is withdrawnthrough line II. This mixture is then introduced into the middle portionof tower 2 where it is subjected to normal distillation. Column 2 may beany conventional type of fractionating column such.

as a bubble type column or packed tower. The mixture introduced intotower 2 through line II is subjected to fractional distillation so thatacetaldehyde and any small amount of hydrocarbons present are takenoverhead and withdrawn through line I2. The bottoms fraction consistingof aldehydes, containing three and more carbon atoms, all ketones,esters etc. are removed from the bottom of the tower through line I3.

Returning now to column I, bottoms liquid withdrawn from the partthereof is passed by line M to a reboiler I5 for heating by heatexchange with a heating medium such as steam. A portion of the bottomsliquid heated and partially vaporized in reboiler I5 is recycled by lineIt to the lower part of column I. The remaining portion of the bottomsliquid is withdrawn through line I1.

The liquid passing through line I1, consisting of alcohols and acids,are passed into tower 3 where it is subjected to distillation to obtaina vapor fraction containing substantially all of the alcohols and abotttoms fraction containing dilute acids. The vapor fraction iswithdrawn through line I8 and passed into distillation column 4 wherecrude methanol of good antifreeze grade is taken out overhead throughline 213. A bottoms fraction is withdrawn from tower 4 through line 2|,consisting of ethyl alcohol and higher alcohols. This fraction may betreated in any conventional manner to separate the ethyl from theremaining alcohols. Returning now to column 3, a bottoms fractionconsisting of dilute acid is withdrawn through line i9 and may bediscarded. However, these dilute acids are useful in supplying the waterused as reflux to tower I. For this reason, it is preferred to recycleacid bottoms from tower 3 to tower I through line 22.

While the above description of the invention has indicated that theessential feature is that the overhead from column I is' essentiallyfree from all alcohol constituents present in the crude organic mixturefed to the column, it is an additional feature of this invention to soregulate operating conditions as regards heat input,

" reflux ratio, feed rates etc. in column I that in addition to thecarbonyls, esters, hydrocarbons, ethers, etc. essentially a majorportion of the branched, secondary and tertiary alcohols present in thehydrocarbon water layer are removed overhead. Thees alcohols consist forthe most part of isopropyl and secondary butyl alcohols.

By this means it is possible to obtain as bottoms a water solution ofacids together with primary alcohols of 1 to 5 carbon atoms essentiallyfree of or greatly depleted in aldehydes, ketones, esters,

9' acetals, hydrocarbons, ethers and branched, secondary and tertiaryalcohols. It; is particularly desirable to remove all the isopropyl fromthe ethyl in which case it may be desirable to remove overhead some ofthe normal butyl and higher normal alcohols.

Referring now to Figure 2, there is shown a modification of theinvention in which the crude aqueous layer is. distilled to removeoverhead everything boiling below the acids and then this overhead isdistilled in the presence of a large excess of aqueous reflux.

Referring, therefore, to this drawing, a fraction having the compositionused in Figure 1 is introduced by line I05 into column I! where it issubjected to ordinary distillation to remove overhead alcohols,aldehydes, ketones and esters which are withdrawn through line I06,leaving an aqueous acid bottoms which are withdrawn through line I01.The overhead vapors are passed through condenser I08 to a receiver I09.

' A portion of the condensate collected in receiver I'09 is returned tothe top of column: I0 I' as external reflux through line H0. Theremaining portion of the distillate collected in receiver I09 iswithdrawn through line III. This mixture is then introduced into themiddle portion of tower I02 where it is fractionated in the presence ofa stream of liquid water introduced through line II2. Conditions aremaintained in tower I02 such as to cause distillation of the oxygenatedcompounds in the presence of the water on each plate of the tower. Asufficient amount of water is added so that it is present to the extentof 90 volume percent on each plate. The operation of column I02 isessentially the same asthat of column I in Figure 1 except that. due tothe preliminary distillation the large volume of water present in thestripping section, is much less, thus resulting in better separationoverhead. Thus the overhead vapors from tower I02 consist of carbonyls,esters, hydrocarbons (if present) and others. These are withdrawnthrough line I I3, condensed in cooler HA: and collected in receiver H5.ceiver H5 is passed by line I I 6 to the top of tower I52 as externalreflux. The remainder is withdrawn through line I'I'l for furtherseparation, if desired.

The aqueous alcohols are withdrawn from the bottom of tower I02 throughline I'l8rior further separation as desired.

If desired a portion. of the aqueous acid bottoms withdrawn through lineI01 may be passed through line H9 and used was the aqueous reflux-introduced through line -I I2.

tilled in the presence of "a. large excess of an aqueous reflux.

Referring, therefore, to this drawing, the overhead from the preliminaryfractionation :zone. il llI obtained as described in connection withFigure 2 is: passed by line HI to a Second fractionation A portion ofthe material in rezone 202 where it is subjected. to ordinaryfractionation. to take overhead methyl alcohol, acetone, acetaldehyde,dimethyl acetal, methyl ethyl ketone, propionaldehyde, butyraldehyde,ethyl alcohol, normal and isopropyl alcohol. ethyl acetate, diethylacetal, secondary butanol, isobutanol, tertiary butanol, isopropylacetate, normal propyl acetate, methyl normal propyl ketone, methylisopropyl ketone, diethyl ketone, methyl isobutyl ketone, ethylpropionate, normal and isovaleraldehyde, methyl normal butyl ketone andlight hydrocarbons. The bottoms fraction will contain in addition tonbutyl alcohol, all the constituents boiling above normal butyl alcohol;Depending upon the exact degree of control efiected and the importanceof freeing the higher normal alcohols of secondary and isobutylalcohols, some n propyl alcohol, secondary and isobutyl alcohols will betaken as bottoms. The overhead fraction is passed by line 203 to themiddle portion of tower 204 where it is fractionated in the presence ofa stream of liquid water introduced through line 205. Conditions aremaintained in tower 204 similar to those maintained in tower I02 ofFigure 2 so as to cause distillation of the oxygenated compounds in thepresence of the water on each plate of the tower. A sufiicient amount ofwater is added so that it is present to the extent of volume percent oneach plate and conditions are maintained sothat the non-alcoholicconstituents present in the fraction fed to the tower are takenoverhead. Thus acetone, acetaldehyde, dimethyl acetal, methyl ethylketone, propionaldehyde, butyraldehyde, ethyl acetate and diethylacetal, isopropyl acetate, n-propyl acetate. methy1-npropyl ketone,methyl isopropyl ketone. diethyl ketone, methyl isobutyl ketone,methyl-n-butyl ketone, ethyl propionate, normal and. iso-valeraldehydeare present in the overhead fraction leaving a solution of alcohols inthe bottom.

Returning now to column 202, the bottoms fraction containing in additionto n-butyl alcohol, all constituents boiling above normal butyl alcohol,any normal propyl and secondary and isobutyl alcohols and tertiary amylalcohol not taken overhead, is passed by line 206 to the midpoint o1tower 231 where it is subjected to fractionation in the presence of astream of liquid water introduced through line 20.8, so that the wateris pres-,- ent to the extent of 90 volume percent on each plate. Theoperation of tower 20! is the same as that of 2M whereby thenon-alcoholic ketones, aldehydes, esters, ketals, acetals and anyhydrocarbons present are taken ofi overhead through line m9 and anaqueous solution of alcohols are removed from the bottom through line2").

A suitable source of aqueous reflux for towers 294 and 261 is the diluteacids removed from the bottom of tower IUI. Accordingly, a portion ofthe bottoms from tower It is passed .by lines 2| I and 2-12 andintroduced to the top of tower 204 through line 205. Similarly anotherportion is passed by lines 2 and 2I3 and introduced into the top oftower 201 through line 208.

Example I A sample of a water layer from a :Eischer synthesis containing84.6 mol percent of alcohols. 1-1.2 mol per cent of carbonyls (ketonesand aldeh-ydes), 0:2. mol percent of esters and 4.0 percent of acids ona water-free basis was distilled in a one inchl. D. perforated platecolumn having 30 plates abovewand 30 plates below the feed point at afeed rate of 485 c. e. per hour, while introducing water as reflux atthe top of the colunm at a rate of 945 c. 0. per hour so that the topplate of the column contained 98 mol percent water. The feed wasintroduced at a temperature of 91" C. and the water at 94 C. Theoverhead temperature was maintained at 84 C. and the reflux ratio at15:1. A total of 6.2% of organic material based on the feed andconsisting of ketones, aldehydes, esters and only a small amount ofalcohols was removed overhead. A bottoms fraction consisting of anaqueous solution of alcohols and acids was withdrawn and passed to asecond distillation zone similar to the first at a rate of 1310 c. e.per hour and a temperature of 91 C. The reflux ratio of the second towerwas 5:1. Alcohols were removed overhead at a temperature of 79 C. Asolution of acids in water were removed from the bottom and returned tothe top of the first column as reflux therein. The following data wereobtained:

ol per cent of component in feed appearing in overhead of extractivedistillation column Feed Example II A sample of the water layer used inExample I was distilled in the same manner as in Example I except thatthe amount of water added was decreased to 930 c. c. per hour tomaintain 96.8 mol percent water on the top plate, the feed rate to thefirst distillation zone was lowered to 440 c. c. per hour, the anhydrousoverhead rate was increased to 8.4 c. c. per hour. By operating in thismanner, 19.1 volume percent of the organic matter in the feed was takenoverhead, including most of the branched secondary and tertiaryalcohols. The following table illustrates the results obtained:

The above data indicates clearly that the undesired impurities presentin the water layer of a product from the Fischer synthesis can beadequately removed by distilling the water layer in presence of a largeexcess of aqueous reflux.

While one specific process involving the novel steps of the presentinvention as well as one specific apparatus for carrying out the samehas been described in detail, it is to be understood that thisdescription is illustrative only and for the purpose of making theinvention clearer, and it is not intended that the invention shall beconstrued as limited to details of the description except insofar assuch limitations have been included in the terms of the followingclaims.

The nature and objects of the present invention having been set forthand specific illustra -tions of the same given, what is claimed as newand useful and desired to be secured by Letters Patent is:

1. The method of separating a mixture of aqueous oxygenated organiccompounds containing at least two normal primary alcohols, branchedalcohols and neutral non-alcoholic oxygenated compounds in the C1 to C5molecular weight range which comprises continuously introducing saidmixture into an intermediate point of a fractionation zone, continuouslyadding sufficient water to the fractionation zone at a pointsubstantially above the mixture feed point to maintain an internalliquid reflux having. a Water content in the range of to 99 mol percentbelow the point of addition of the water, distilling from the mixturevapors of the oxygenated compounds which flow countercurrent to theaqueous reflux, removing overhead from the fractionation zone an aqueousdistillate consisting of the neutral non-alcoholic oxygenated compoundsand the branched a cohols and recovering as bottoms from thefractionation zone an aqueous solution consisting of the normal primaryalcohols.

2. The methods of separating a mixture of a ueous oxvgenated organic comounds containing at least two normal primary alcohols, branchedalcohols, neutral non-alcoholic oxygenat d compounds and acids in the C1to C5 molecular weight range which comprises continuously introducingsaid mixture into an intermediate point of a fractionation zone,continuously adding sufficient water to the fractionation zone at apoint su stantially above the mixture feed point to maintain an internalliquid reflux having a water content in the range of 85 to 99 mol percent below the point of addition of the water, distilling from themixture vapors of the oxygenated compounds which flow countercurrent tothe aqueous reflux, removing overhead from the fractionation zone anaqueous distillate consisting of the neutral nonalcoholic oxygenatedcompounds and the branched alcohols, and recovering as bottoms from thefractionation zone an aqueous solution consisting of the normal primaryalcohols and acids.

3. A process according to claim 2 in which the aqueous solutionrecovered from the fractionation zone is fractionated in a secondfractionation zone to produce an overhead distillate of alcohols and abottoms of a ueous acid which is recycled as water reflux to the firstfractionation zone.

4. The method of separating a, mixture of aoueous oxygenated organiccompounds containing at least two normal primary alcohols, branchedalcohols, neutral non-alcoholic oxygenated compounds and acids in the C1to C5 molecular weight range which comprises introducing the mixtureinto a first fractionation zone, removing overhead from the firstfractionation zone a distillate comprising substantially all of theneutral non-alcoholic oxygenated compounds and all the alcohols,removing a bottoms product from the first fractionation zone comprisingsubstantially aqueous acids, introducing the overhead from the firstfractionation zone into an intermediate point of a second fractionationzone, continuously adding sufficient aqueous acid bottoms from the firstfractionation zone to the second fractionation zone at a pointsubstantially above the overhead feed point to maintain an internalliquid reflux having a water content in the range of 85 to 99 mol percent below the point of addition of the aqueous acid bottoms, distillingfrom the mixture vapors of the oxygenated compounds which flowcountercurrent to the aqueous acid reflux-removing overhead from thesecond fractionation zone a distillate consisting of the neutralnon-alcoholic oxygenated compounds and the branched alcohols, andrecovering as bottoms from the second 13 fractionation zone an aqueoussolution consistin of the normal primary alcohols and acids.

5. The method of separating a mixture of aqueous oxygenated organiccompounds containing at least two normal primary alcohols, branchedalcohols, neutral non-alcoholic oxygenated compounds and acids in the C1to C5 molecular weight range which comprises introducing said mixtureinto a, first fractionation zone, removing overhead from said firstfractionation zone the alcohols and the neutral nonalcoholic oxygenatedcompounds, recovering bottoms from the first fractionation zonecomprising an aqueous solution of the acids, introducing the overheadfrom the first fractionation zone into an intermediate point of thesecond fractionation zone, fractionating said overhead in the secondfractionation zone to obtain a distillate comprising all compoundsboiling within the range of the normal alcohols having A carbon atomsper molecule and a bottoms fraction comprising all compounds boilingwithin the range of normal alcohols having B carbon atoms per molecule,passing the A fraction into an intermediate section of a thirdfractionation zone,

neutral non-alcoholic oxygenated compounds and branched alcohols havingB carbon atoms per molecule respectively, and recovering as bottoms fromthe third and fourth fractionation zones an aqueous solution consistingof the nor mal primary alcohols having A carbon atoms per molecule andnormal primary alcohols having B carbon atoms per molecule respectively.

6. A process according to claim 5 in which A is 1 to 3 and B is 4-5respectively.

'7. A process according to claim 5 in which A is 1 to 2 and B is 3-5respectively.

8. A process according to claim 5 in which A is C1-C3 and B is C3-C5respectively.

CHARLES E. MORRELL. CARL S. CARLSON. PAUL V. SMITH, JR.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 996,328 Guillaume June 27, 19111,929,901 Ricard et al Oct. 10, 1933 1,933,505 Merley Oct. 31, 19332,179,991 Bright et a1. Nov. 14, 1934 2,198,651 Bludworth Apr. 30, 19402,283,911 Brant et a1. May 26, 1942 2,290,442 Metzl July 21, 19422,290,636 Deanesley A July 21, 1942 2,324,755 Beamer July 20, 19432,364,341 Bright et a1 Dec. 5, 1944 2,551,584 Carlson et a1 May 8, 19512,551,626 Morrell et a1 May 8, 1951

1. THE METHOD OF SEPARATING A MIXTURE OF AQUEOUS OXYGENATED ORGANICCOMPOUNDS CONTAINING AT LEAST TWO NORMAL PRIMARY ALCOHOLS, BRANCHEDALCOHOLS AND NEUTRAL NON-ALCOHOLIC OXYGENATED COMPOUNDS IN THE C1 TO C5MOLECULAR WEIGHT RANGE WHICH COMPRISES CONTINUOUSLY INTRODUCING SAIDMIXTURE INTO AN INTERMEDIATE POINT OF A FRACTIONATION ZONE, CONTINUOUSLYADDING SUFFICIENT WATER TO THE FRACTIONATION ZONE AT A POINTSUBSTANTIALLY ABOVE THE MIXTURE FEED POINT TO MAINTAIN AN INTERNALLIQUID REFLUX HAVING A WATER CONTENT IN THE RANGE OF 85 TO 99 MOLPERCENT BELOW THE POINT OF ADDITION OF THE WATER, DISTILLING FROM THEMIXTURE VAPORS OF THE OXYGENATED COMPOUNDS WHICH FLOW COUNTERCURRENT TOTHE AQUEOUS REFLUX, REMOVING OVERHEAD FROM THE FRACTIONATION ZONE ANAQUEOUS DISTILLATE CONSISTING OF THE NEUTRAL NON-ALCOHOLIC OXYGENATEDCOMPOUNDS AND THE BRANCHED ALCOHOLS AND RECOVERING AS BOTTOMS FROM THEFRACTIONATION ZONE AN AQUEOUS SOLUTION CONSISTING OF THE NORMAL PRIMARYALCOHOLS.